The water mite family Aturidae Thor, 1900 from Southeast Asia (Acari: Hydrachnidia) with the description of one new genus and 14 new species

A BSTRACT — New records are given of members of the water mite family Aturidae from Thailand and Malaysia. The subgenus Javalbicula K.O. Viets, 1974 of the genus Javalbia is synonymized with Javalbiopsis Cook. One new genus is described, viz . Siamaxonopsis n. gen., and the following new species are described: Albaxona elongata n. sp., Brachypodopsis thailandicus n. sp., Hexaxonopsis reticulata n. sp., H. monouncata n. sp., Javalbia discrepans n. sp., J. lineata n. sp., J. siamis n. sp., J. magna n. sp., J. nova n. sp., J. rotunda n. sp., Paraxonopsis separata n. sp., Siamaxonopsis ypsilon n.sp., Sinaxonopsis siamicus n. sp. and Vicinaxonopsis costata n. sp. A (partial) redescription is given for the male of Brachypodopsis baumi (Halík). The female of Javalbia solitaria Smit and Peši´c is described for the ﬁrst time. New records are given for the genera Aturus Kramer, Axonopsis Piersig, Brachypodopsis Piersig, Javalbia Viets and Albia Thon from Thailand and/or Malaysia. K EYWORDS


INTRODUCTION
The water mite family Aturidae has a worldwide distribution. Currently, the family has four subfamilies, Aturinae Thor, 1900, Albiinae Viets, 1915, Axonopsinae Viets, 1929and Notoaturinae Besch, 1964. Apart from the latter subfamily, which has a Gondwanan distribution, all subfamilies occur worldwide. Cook (1974) stated that the Aturidae are a "dumping ground" of mites with heavily sclerotized idiosoma, which cannot be assigned to other families. Also the subfamily classification is not satisfactory, as there are species known nowadays which bridge the gap between the two subfamilies. Even the separation with the Hygrobatidae is not always clear (Cook 1974).
In the Oriental region aturids are a major part of the water mite fauna. Smit and Pešić (2014) found that 30 % of their specimens from Borneo were aturids. On a generic level, however, it is not the richest faunal region (Di Sabatino et al. 2008). Large areas of the Oriental region, however, are understudied. Pešić and Smit (2015) published a checklist of the water mites of Thailand. Aturids were lacking in this checklist, but the records of Piersig (1906) were not included. Therefore the following species should be added to the checklist of Thailand: Hydrachna semiscutata Piersig, 1906, H.volzi Piersig, 1906, Neumania (Ecpolopsis) multiscutata (Piersig, 1906) (Unionicolidae), Piona pachydermoidea Viets, 1956 (Pionidae) and Brachypodopsis coerulea Piersig, 1906 (Aturidae). This paper deals with collections of water mites from Thailand and Malaysia. For the generic classification Smith et al. (2015) is followed. Female Smit H. aturids are sometimes difficult to identify, especially when no specific characters are present, and a number of specimens are left undescribed.

MATERIALS AND METHODS
All material has been collected by the author. Type material and non-type material is lodged in Naturalis Biodiversity Center, Leiden. Numbers are given as males/females/deutonymphs. The following abbreviations have been used: P1-P5 = palp segment 1-5; Cx-I = first coxal plates; cxgl-4 = coxoglandularium 4; vgl-4 = ventroglandularium 4; Ileg-4-6 = fourth-sixth segments of first leg; A2 = postantenniform glandularia; dgl-1 = dorsoglandularia 1; a.s.l. = above sea level; L = length; W = width; NP = National Park. Measurements of paratypes are given in brackets. All measurements are in µm, measurements of palp and leg segments are of the dorsal margins. Length of the venter is measured from the tip of the first coxae till the posterior idiosoma margin. Coordinates were obtained with a GPS. When no measurements were made or were not possible, coordinates are derived sometimes from Google Earth (given as degrees and minutes).

SYSTEMATICS
Family Aturidae Thor, 1900 Subfamily Aturinae Thor, 1900 Genus Aturus Kramer, 1875 The genus Aturus is widespread, and occurs in all faunal regions except Australasia. Within the Oriental region they have been reported from Java, India, South Korea and Borneo (Viets 1935;Cook 1967;Lundblad 1971;Chung 1993, 1995;Smit and Pešić 2014). Unfortunately, only females have been collected, and males are necessary to identify or describe the species. As the genus has not been reported previously from Thailand and Malaysia, I will give the locations where these females have been collected. Genus Bharatalbia Cook, 1967 From the genus Bharatalbia ten species are known from India, Japan, Malaysia and the USA (Smith et al. 2015, Wiles 1991

Subfamily Axonopsinae Viets, 1929
Genus Albaxona Szalay, 1944 The genus Albaxona is widely distributed, and known from the Palaearctic, Oriental, Ethiopian and Nearctic regions (Cook 1974 with three acetabula on the right side and two acetabula on the left side. Acetabulum 2 lying directly posterior to acetabulum 1. Vgl-4 not fused with ventral shield. Excretory pore on a small platelet posterior to and not fused with postgenital sclerite. Length of 36,27,51,58,70,58. Legs without swimming setae. Male: Unknown.
Etymology -Named for its slender idiosoma.
Remarks -The lack of one acetabulum is a phenomenon observed in other aturid genera as well, e.g. in Javalbia (Smit and Pešić 2014). However, it may be expected that normally three pairs will be present in a configuration as shown in the right side of the genital field. Due to its small size and the configuration of the acetabula, the new species is most close to Albaxona hexapora (Viets, 1935) from Java. However, the new species is more slender, L/W of the idiosoma is 1,26 in A. hexapora and 1,32 in the new species. Albaxona kurtvietsi Gledhill and Wiles, 1997 from Sri Lanka is another small species. This species has the acetabula lying in a line and the postocularia are lying closer to dgl-1 compared to the new species.

Genus Axonopsis Piersig, 1893
The genus Axonopsis is widespread and only absent from Australasia and the Neotropical regions (Smith et al. 2015).

Axonopsis gracilipalpis Viets, 1935
Material examined -Thailand. Remarks -Previously known from Java and Borneo (Viets 1935, Wiles 1999, Smit and Pešić 2014 and here reported for the first time for Thailand.

Genus Brachypodopsis Piersig, 1903
The genus Brachypodopsis is widespread, and absent only from the Australasian region (Smith et al. 2015).

Subgenus Brachypodopsis Piersig, 1903
Brachypodopsis baumi (Halík, 1930) ( Description -Male: Idiosoma yellowish, dorsally 389 long and 320 wide. Dorsal shield 300 wide, posteriorly tapering, anteriorly fused with ventral shield, with six pairs of glandularia. Dorsal furrow lacking glandularia. Postocularia slightly posteromedially of dgl-1; excretory pore fused with dorsal shield. In anterior part of dorsal shield a drop-shaped structure visible. Suture lines of coxae obliterated. A lateral ridge extending anteriorly of fourth leg sockets. Between fourth leg sockets and genital field two pairs of glandularia present, one pair very close to genital field. Genital field terminal, with three pairs of acetabula. Palp not mounted and measured. Length of I-leg-4-6: 44, 50, 54. Length of IV-leg-4-6: 68, 66, 54. Legs not modified. III-leg-5 and IV-leg-5 with three swimming setae, IV-leg-4 with one swimming seta. Remarks -Brachypodopsis baumi is insufficiently described, and therefore a redescription is given for the male. Halík (1930) didn't illustrate the pair of glandularia close to the genital field (although these were mentioned by Cook 1967). The male of Lam Takhong Creek is here described. This is a widespread species, known from Malaysia, Burma, Java and Borneo and here reported for the first time from Thailand. Diagnosis -Genital field with four pairs of acetabula, anterior three pairs in a line more or less perpendicularly to lateral idiosoma margin. Dorsal shield with A2 and six pairs of glandularia. Between the fourth leg sockets and genital field two pairs of glandularia.
Description -Female: Idiosoma brownish, dorsally 454 long and 332 wide, ventrally 421 long. Dorsal shield 332 wide, anteriorly fused with ventral shield, and with A2 and six pairs of glandularia (the most posterior pair not visible in dorsal view). No glandularia platelets present in dorsal furrow. Postocularia far distanced from dgl-1; excretory pore fused with dorsal shield. Anterior coxae distanced from anterior idiosoma margin, coxal suture lines obliterated. A ridge present anterolaterally of fourth leg sockets. Between the fourth leg sockets and genital field two pairs of glandularia, these lying closer to genital field than to fourth leg sockets. Genital field with four pairs of acetabula, the anterior three pairs in a line more or less perpendicularly to lateral idiosoma margin. An undulating ridge present between anterior three pairs and most posterior pair of acetabula. Gonopore large, 80 long and 102 wide. Length of P1-5: 26, 50, 26, 68, 28. P4 lineated, without heavy setae, but maybe broken off. Length of I-leg-4-6: 45, 66, 70 (till tip of segment). Length of IV-leg-4-6: 70, 84, 76.   Swimming setae: III-leg-4 and IV-leg-4 two, III-leg-5 four and IV-leg-5 three. Male: Unknown.
Etymology -Named after the country where the species was collected.
Remarks -The new species is assigned to the genus Brachypodopsis due to the absence of glandularia platelets in the dorsal furrow, the presence of seven pairs of glandularia on the dorsal shield and two pairs of glandularia between the fourth leg sockets and genital field. The new species is somewhat similar to Paraxonopsis vivarna (Cook, 1967) from India in the configuration of the acetabula. However, this species has the dorsal shield with four pairs of glandularia and only one pair of glandularia between the fourth leg sockets and genital field. Due to the absence of a male subgeneric placement of the new species is not possible.

Genus Hexaxonopsis Viets, 1926
A widespread genus, but not reported from the Neotropical and Australasian regions (Smith et al. 2015).
Diagnosis -Central dorsoglandularia pair closer to each other than other dorsoglandularia pairs.
Remarks -All similar Hexaxonopsis species (e.g. H. bharatensis (Cook, 1967), H. alpa (Cook, 1997) and H. niraensis (Cook, 1967)), have two dorsal (third and fourth) pair of glandularia close to each other, while in the new species such closely lying glandularia are absent. Moreover, the fourth pair of dorsal glandularia lying much closer to each other is not found in other Hexaxonopsis species.

Subgenus Plesiobrachypoda Viets, 1942
A subgenus with thus far only two species known from Sudan and India (Smith et al. 2015).
Etymology -Named for the presence of only one pair of coxal hooks.
Remarks -The two other Plesiobrachypoda species have both the first and second coxae drawn into hooks. Axonopsis periyar Pesic and Ranga Reddy, 2009 from India has very stocky IV-leg-5 and-6 (Pesic and Ranga Reddy 2009).

Genus Javalbia Viets, 1935
The genus Javalbia is known from Europe (two species), Turkey (one species) and Africa (two species), but most species are known from the Oriental region (13 species). Especially the high number of eight species from Borneo is striking (Smit and Pešić 2014). Two "Axonopsalbia" species described by Cook (1967) from India might as well belong to this genus.
Four subgenera are known currently, i.e. Javalbia, Javalbiopsis Cook, 1967, Javalbicula K.O. Viets, 1974 andMegapes Smit andPešić, 2014. The subgenus Javalbicula differs only in the number of acetabula (four pairs instead of three). The two Asian species, i.e. J. ovata Kim and Chung, 1996 and the 4-acetabulate species described below, have the excretory pore on a separate platelet. The African species J. lata K.O. Viets, 1974 and the Turkish J. turcica Esen, Pešić and Erman, 2011 have the excretory pore fused with the dorsal shield (K.O. Viets andBöttger 1974, Esen et al. 2011). Therefore I propose to synonymize Javalbicula with Javalbiopsis, and assign the two Asian species to Javalbia s.s. Etymology -Named for the very different dorsal shield compared to other Javalbia species.

Subgenus
Remarks -The dorsal shield with a posterior extension is not found in any other Javalbia species. Moreover, the fused glandularia platelets in the dorsal furrow are also unique. Javalbia lineata n. sp. (Figure 7) Material  Etymology -Named after the old name for Thailand.
Remarks -The new species differs from J. ovata Chung, 1996 from Korea (Kim andChung 1996) in the free-lying anterolateral dorsal glandularia (fused in J. ovata), and the postocularia distanced and posteromedially from the nearest pair of dorsal glandularia (lying much closer and at the same line of glandularia pair). Remarks -In all characters the male specimen of this study is identical with the holotype (and thus far only known specimen) from Borneo (configuration of the dorsal glandularia and postocularia, anterolateral pair of dorsal not fused with dorsal shield, relatively wide gonopore, vgl-4 fused with ventral shield). The female is described here for the first time. Etymology -Named for its relatively large size.
Etymology -An obvious name for a new species.
Remarks -The combination of the postocularia lying anteromedially of dgl-1, A2 not fused with the dorsal shield and the setae of dgl-2 distanced is characteristic for the new species, and not found in any other member of Javalbiopsis. Diagnosis -A2 not fused with dorsal shield; postocularia lying anteromedially of dgl-1; dgl-4 absent, only associated setae present; anterior coxae close to anterior idiosoma margin; gonopore nearly rounded.
Etymology -Named for the nearly rounded gonopore.
Remarks -Few Javalbiopsis species have the postocularia anteromedially of dgl-1: Javalbia kinabaluensis Smit and Pešić, 2014 has the genital field separate from the ventral shield, J. magniseta Smit and Pešić, 2014 has very large dorsal setae and the coxae lying less anteriorly, J. reticulata Smit and Pešić, 2014 has a less rounded gonopore and dgl-2 and -3 without glandularia and J. nova n. sp. has dgl-4 with glandularia.

Genus Paraxonopsis Motaş and Tanasachi, 1947
A widespread genus absent only in Australasian and the Neotropical regions (Smith et al. 2015) Paraxonopsis separata n. sp.
Etymology -Named for the widely separated acetabula.
Remarks -None of the known four-acetabulate Paraxonopsis species has the acetabula separated as widely as in the new species.

Genus Siamaxonopsis n. gen.
Diagnosis -Dorsal and ventral shields present. Dorsal shield fused anteriorly with ventral shield. Dorsal shield with A2, postocularia and four pairs of glandularia, the most posterior pair flanking the excretory pore (the latter fused with dorsal shield) and visible only in posteromedial view. Anterior coxal plates not extending to anterior idiosoma margin, without hook-like structures. Anterior to fourth leg sockets a ridge extending to lateral idiosoma margin. Between fourth leg sockets and genital field with two pairs of glandularia, lying closer to genital field than to fourth leg sockets. Genital field numerous pairs of acetabula. P2 with a large nose-shaped extension.
Etymology -Named for the Y-shaped structures on the dorsum.

Genus Sinaxonopsis Yi and Jin, 2012
From the recently described genus Sinaxonopsis one species is known only from Anhui Province, China (Yi and Jin 2012). A second species is described below. Diagnosis -Ridge anterolaterally of fourth leg sockets very short; setae associated with dgl-2 and dgl-3 distanced from glandularia; lgl-2 not on large posterior dorsal shield, lgl-3 and -4 on small humps. Description -Female: Idiosoma colourless, dorsally 429 long and 389 wide, ventrally 429 long. Dorsum with three plates, smaller paired anterior plates and a large unpaired posterior plate. Anterior plates with the postocularia and two pairs of glandularia, posterior plate with five pairs of glandularia. Setae associated with dgl-2 and dgl-3 distanced from glandularia. This large posterior pair fused to ventral shield, but most of the posterior part of the dorsal furrow not visible due to rugosity of the idiosoma. Suture lines of coxae incomplete, first coxae not extending beyond anterior idiosoma margin, posterior margin of fourth coxae incomplete. Cxgl-4 lying posterior to fourth leg sockets. Excretory pore posterior to genital field but visible only in dorsal view. Gonopore relatively large, 102 long. Genital field with approximately 20 pairs Smit H. FIGURE 14: Sinaxonopsis siamicus n. sp., holotype female: A -dorsum; B -venter; C -palp; D -IV-leg-4-6. Scale bars = 50 µm.
Etymology -Named after the old name of Thailand.
Remarks -The new species differs from S. unicucrus Yi and Jin, 2012 in the smaller size (564 -594 for S. unicucrus), A2 posteromedially of dgl-1 (A2 anteromedially of dgl-1 in S. unicucrus) and the characters mentioned in the diagnosis of the new species. Yi and Jin (2012) placed the new genus tentatively in the Axonopsinae, which is a correct placement in my opinion.

Genus Vicinaxonopsis Cook, 1974
The genus Vicinaxonopsis is known from the Holarctic and Oriental regions (Smith et al. 2015). Diagnosis -Eyes absent, venter with distinctive longitudinal ridges.

Description -Female:
Idiosoma brown coloured, dorsally 489 long and 373 wide, ventrally 467 long; eyes absent. Dorsal shield fused anteriorly with ventral shield, 373 wide; excretory pore fused with dorsal shield. Dorsal shield with A2, postocularia and four pairs of glandularia; due to rugosity of integument associated setae of dorsoglandularia not visible. Body pores of integument arranged in a rounded pattern in anterior part of dorsal shield; anterior part of dorsum with two pairs of large lateral papillae. Anterior coxae not extending to anterior idiosoma margin. Coxal suture lines obliterated. Apodemes of gnathosoma very long. Anterior to the fourth leg sockets a ridge extending to the lateral idiosoma margin. Venter with numerous distinctive longitudinal ridges. Between fourth leg sockets and genital field two pairs of glandularia, lying close to each other. Genital field with three pairs of acetabula; gonopore 60 long and 46 wide. Length of P1-5: 30, 50, 24, 50, 53. P4 stocky and ventrally somewhat bulging, with a long ventral seta; P5 long and slender. Length of I-leg-4-6: 52, 54, 56 (till tip of segment). Length of IV-leg-4-6: 80, 78, 56. Numbers of swimming setae: IV-leg-4 one, IV-leg-5 two. Male: Unknown.
Etymology -Named for the distinctive ridges of the venter.
Remarks -The combination of absence of eyes and the presence of longitudinal ridges is characteristic for the new species. Vicinaxonopsis caeca (Smit and Pešić, 2014) from Borneo has reduced lateral eyes and a different patterns of the anterior dorsal shield (Smit and Pešić 2014). Despite the absence of eyes, the distinctive brown colour of the idiosoma shows that this species is not hyporheic.